Threaded container closure

ABSTRACT

A threaded container closure assembly having at least one element made of a resilient plastic material. Threads are provided on one element which are received in corresponding recesses provided on the other closure element. A plurality of integrally formed projections are provided on one of the elements to provide increased frictional engagement between the closure elements.

United States Patent Baugh 1 [451 Aug. 8, 1972 [54] THREADED CONTAINERCLOSURE 3,405,831 10/1968 Hudson ..215/43 [72] Inventor; William A.Baugh, overland park 3,556,334 1/1971 Howard ..215/43 Kan-M6204"P'maryExa 1.1 dLKin A n nu ro [73] Ass1gnee: gthylMDevelopment CorpKansas Assistant g gulp, JL

Attorney-Donald L. Johnson, John F. Sieberth, E. [22] .Filed: June 15,1970 Donald Mays and Arthur G. Connolly [21] Appl.No.: 46,1 14 ABSTRACT52 us. 01. .215/43 1:,220/39 R A thread! clmufe assembly having at least51 1111. C1. ...B65d 41/04 one element made of a resilient P1219"cmaterial- 58 Field of Search ..215/43 R, 1 c; 220/39 R, Threads 9Provided on one element which are Dig 14 recelved in correspondingrecesses prov1ded on the other closure element. A plurality ofintegrally formed [56] References Cited projections are provided on oneof the elements to provide increased frictional engagement between theUNITED STATES PATENTS closure e1emems 3,297,185 1/1967 Plymale ..215/433,295,708 1/1967 Wathen ..215/43 1 clamsnnw'ngfigum 3,297,213 1/1967Henderson...; ..2l5/43 X PATENTEUAUG 8 m2 SHEET 1 OF 2 FIG. I

FIG. 3

FIG. 2

PATENTED 9 I97? 3 682 345 sum 2 OF 2 FIG. 5

THREADED CONTAINER CLOSURE BACKGROUND OF THE INVENTION closure elements.

2. Description of the Prior Art In containers utilizing threadedclosures wherein resilient plastic material. A plurality of spaced apartprojections are integrally formed on one of the eleeither the containeror closure or both are fabricated froma resilient plastic material suchas polyethylene, polyvinyl chloride, or polypropylene, difficulty isencountered in maintaining a fluid-tight closure. Resilientthermoplastic materials inherently possess the ability to cold flowunder pressure which results in a gradual loosening of the container capon the neck of the container. Additionally, the low coefficient offriction possessed by many of the commercially used plastic materialsincreases the tendency of the container 010- sure to gradually becomeloosened.

Numerous locking or friction-increasing devices for container closureshaving plastic elements have been proposed for solving this problem. InUS. Pat. No. 3,295,708 a threaded closure is provided which includes asmall projection or lug upon the top surface of the upper end of thethread on the plastic container. U.S. Pat. No. 3,435,978 discloses aclosure system for containers wherein the threads on the bottle and thecap are interlocked by means of a detent or by means of offset segmentsin the threads. The container closure system as shown in US. Pat. No.3,405,831 has flexible protrusions extending radially outward from thethreads of the container neck to provide a jamming action in thethread-receiving grooves of the cap when the cap is screwed onto thecontainer neck.

While the foregoing and other closures have proved satisfactory in manyrespects, nevertheless, there is still a need for a container closurewhich provides for longterm retention of the initial torque used toapply the cap. The present invention provides a closure assembly whichresists subsequent loosening of the cap from either internal pressure ofthe packaged product or from normal relaxation and cold flow of theresilient plastic of the container or closure.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a threaded closure construction which provides a tight,leakproof closure.

It is also an object of the present invention to provide a threadedclosure construction which resists loosening during shipment yet whichcan be readily separated by hand.

It is a further object of the present invention to provide a threadedclosure assembly having components which are readily formed in themanufacture of the container and the closure caps.

The foregoing objects are provided for in a threaded joining meansincluding a male element having spiral threads on its exterior surface.A female element is provided having complementary means on its interiorsurface for engaging the spiral threads of the male element. At leastone of the elements is formed from a ments and frictionally engage theother element to resist relative movement between the elements.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of acontainer having a neck section embodying the present invention;

FIG. 2 is a vertical sectional view of the threaded neck section of acontainer with a cooperating cap assembled thereto utilizing the presentinvention;

FIG. 3 is a vertical sectional view taken along line 3-3 of FIG. 1;

FIG. 4 is a cross sectional view taken along line 4-4 of FIG. 1;

FIG. 5 is an enlarged, perspective, elevational view of a portion of thethread of the container of FIG. 1;

FIG. 6 is a sectional view taken along line 66 of FIG. 5;

FIG. 7 is a vertical sectional view of a container cap for use in thepresent invention; and

FIG. 8 is an enlarged cross sectional view taken along line 88 of FIG.2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, acontainer, designated generally by the reference numeral 10, is providedwith a body portion 11 and a generally cylindrical neck portion 12.While the body portion of the container is generally depicted ascylindrical, it is understood that the body may have any form desirable,e.g., elliptical, spherical, or any other desired shape. The neck 12 isprovided with an integrally formed, external, helical thread 13. Whilethe thread illustrated in the drawing is a buttress thread, it isunderstood that any shape thread desired may be used in conjunction withthe present invention. As can be seen more clearly in FIG. 5, the thread13 is provided with a downwardly inclined top surface 13a, asubstantially vertical side surface 13b, and an inwardly inclined lowersurface 130. The thread may extend from the top of the container neck tothe lower extremity of the container neck as depicted in FIG. 1.However, if desired, the thread may be provided only over theintermediate portion of the container neck. Also, instead of acontinuous thread, interrupted threads may be utilized.

The container may be formed of a rigid material such as metal or glassof a flexible or resilient material such as plastic. In the event thatthe container is made by blow molding or injection molding athermoplastic material such as polyethylene, polypropylene, or polyvinylchloride, the neck and threads may be integrally formed on thecontainer. However, the neck and thread section may be separately formedand attached to the container top by conventional means such as utilizedin the manufacture of plastic squeeze tubes.

In the container depicted in FIGS. l4, the thread 13 is provided with aplurality of integrally formed projections or lugs 14 extendingdownwardly from the lower surface 130. As may be seen in FIG. 4, eachconvolution of the thread 13 is provided with four evenly spaced apartprojections 14. The projections are arranged in four vertically alignedrows. However, it is not essential that the projections be aligned orthat they be evenly spaced. Any number of projections can be utilized atany desired position.

As seen more clearly in FIGS. 5 and 6, the projection 14 extends a shortdistance below the lower surface 130 of the thread and terminates shortof the sidewall 13b of the thread. The projection is depicted as havingthe general form of an equilateral triangle; however, it is understoodthat other shapes may be used such as semicircular, elliptical,rectangular, or other suitable shapes. The outer end 14a of theprojection is generally rounded and blends into the lower wall 130 ofthe thread short of the outer wall 13b. Thus, the projection has alength less than the depth of the thread 13. While as mentioned abovethe projection 14 can have any shape desired, the triangular shape shownin the draw ing is preferred. The triangle may have an included anglealpha from about 45 to about 90. However, a 90 angle is preferred.

The closure cap designated generally by the numeral 15 may be formed ofeither rigid or flexible material such as metal or plastic. When the capis used with a rigid container such as glass, the cap should be formedof a resilient material such as high density polyethylene, polypropyleneor other suitable semirigid plastic material which has the ability todeform under pressure. When the cap is used with a container having aneck and threads made of a deformable plastic, the cap may be formedfrom metal or from a rigid plastic material such as a phenolformaldehyderesin, polycarbonates, polyacetals, acrylonitrilebutadiene-styreneresins and others. It is essential that at least one of the elements,i.e., the threaded container neck or the cap, utilized in he closure ofthe present invention be formed of a resilient material having theability to deform under pressure. If desired, both the cap and the necknd threads of the container may be formed from plastic material.However, at least one of the elements should be formed from athermoplastic material having the ability to deform under pressure.

The cap of FIG. 2 includes a top 16 and an integrally formed dependingside skirt 17. A continuous spiral thread-receiving groove 18 isprovided in the interior wall 19 of the cap. If desired, instead ofutilizing a groove in the interior wall, the cap may be made with anintegrally formed, raised, matching thread on its interior wall whichwill mesh with the thread 13 provided on the container neck. The groove18 is of the same general size and shape as the thread 13 to provide aclose sliding fit.

In the embodiment of the invention seen in FIGS. 2 and 3, the neck 12,integrally formed threads 13, and the cap 15 are formed of resilientplastic material. When the cap is screwed onto the container neck, thethread-receiving grooves 18 deform to pen'nit the projections 14 toslide therethrough as the cap is screwed onto the neck. Additionally,the lugs 14 will be slightly compressed and flattened into theundersurface 130 of in the cap at their points of contact resulting in adepression 22 in the lower wall of the thread-receiving groove 18provided in the cap skirt 17. The interlocking between the projections14 and the depressions 22 prevent loosening of the cap after it isscrewed down tight on the container neck.

A different embodiment of the cap is depicted in FIG. 7. The cap,designated generally 24, has a top wall 25 and a depending skirtsidewall 26. The interior wall 27 of the skirt is provided with acontinuous threadreceiving groove 28. A plurality of projections 29 areintegrally formed on nd project upward from the lower wall ofthread-receiving groove 28. The projections as shown in FIG. 7 arearranged in four evenly spaced vertical rows on the interior sidewall ofthe cap. However, as in the case of the threads on the container neck,it is not required that the projections be evenly spaced or arranged inrows. The cap 24 is formed from a resilient plastic material such ashigh or medium density polyethylene, polypropylene, semirigid polyvinylchloride or other plastic material which has sufiicient resiliency todeform or cold flow under moderate pressure. The cap may be made byinjection molding, vacuum forming, blow molding, thermoforming or anyother suitable means. This embodiment of the cap of the presentinvention is particularly adapted for use on containers having threadednecks made from a rigid material such as glass or metal. However, thisembodiment of the cap may also readily be used on containers havingnecks and threads made from a resilient plastic material such as high ormedium density polyethylene or polyvinyl chloride. While the closure ofthe present invention provides satisfactory results when only one of theclosure elements is made from a resilient plastic material, it ispreferred for best results to fabricate both the container neck andthreads and the cap from a resilient plastic material. Particularlysuitable combinations are achieved by forming the container from mediumor high density polyethylene and the cap from low density polyethyleneor polypropylene.

Conventionally, plastic caps are applied to plastic containers with atorquing force of about 15-16 inch pounds. Any torquing force in excessof this will usually result in stripping the threads or attaching thecap to the container with such force that it cannot be convenientlyremoved by hand. After relaxation of the internal stresses in theplastic material, it has been found that the removal torque required toremove a conventionally threaded plastic cap from a plastic containervaries from about 3 to about 8 inch pounds.

Tests were conducted with the container closure of the present inventionto determine if the closure would prevent leakage and also to determinethe torque force required to remove the container cap. The test bottleswere blow molded from high density polyethylene and equipped with thebuttress threads having integrally formed projections as shown inFIG. 1. The projections were 0.008 inch high and terminated 0.005 inchshort of the outer wall of the thread. They were triangular in shape andhad an included angle of The bottles had a nominal fluid capacity of 4ounces and were generally cylindrical in shape. Commercial caps madefrom low density polyethylene and having a matching threadreceivinggroove were utilized. Ten bottles were filled with 2 ounces of acommercial cream peroxide and the caps were applied with a torquingforce of 15-16 inch pounds. The sample bottles were placed horizontallyin a circulating air oven and held at 120 F. (5 F.) for 24 hours. Thistime and temperature have been found to be substantially equal toapproximately 90 days shelf storage at ambient temperature. Ten controlsamples were prepared using the same cap on the same size bottle whichdid not include locking lugs of the present invention of the neckthreads. At the end, of the test period, it was found that no leakagehad occurred in the test bottles equipped with the locking lugs of thepresent invention. Three of the control samples showed definite signs ofleakage. The caps were removed from all bottles and the torquing forcerequired for removal was recorded. The torque force required on thebottles equipped with the device of the present invention ranged from6.5 to 8.0 inch pounds and had an average of 7.35 inch pounds. The capswere also removed from the 10 control samples and were found to requirea torque removal force from 3.5 to 7.0 inch pounds and averaged 5.35inch pounds.

From the foregoing it can be seen that the closure of the presentinvention provides a liquid and vapor-proof seal for holding high vaporpressure products. Additionally, the test data indicate that the torqueforce required to remove the cap from the closure system of the presentinvention is within the range normally considered acceptable bypackagers. The closure system of the present invention is readilyadaptable to high speed, large scale manufacture of containers and theirclosures. Additionally, the closure system can be used with conventionalhigh speed automatic closing equipment without any further modificationsto the equipment.

the art that various modifications and changes may be made withoutdeparting from the essence of the invention. It is intended to coverherein all such modifications and changes as come within the true scopeof the following claims.

What is claimed is:

1. In a container and closure therefor, the combination comprising: ahollow upstanding neck portion on said container; a spiral screw threadintegrally formed on said neck portion; a plurality of integrallyformed, triangularly shaped projections having an included angle of fromabout 45 to about projecting from the underside of said spiral screwthread, said projections having an arcuate shaped outer end; a closuremember having a top portion and a depending skirt portion, said skirtportion having a continuous spiral groove in its interior wall adaptedto receive said-spiral screw thread and said projections; and at leastone of the group consisting of said container and said closure memberbeing formed of a resilient plastic material whereby either saidprojections or said spiral groove in said closure member are deformed bycold flow to produce aninterlocking between said container and saidclosure member thereby preventing leakage between said container andsaid closure member.

1. In a container and closure therefor, the combination comprising: ahollow upstanding neck portion on said container; a spiral screw threadintegrally formed on said neck portion; a plurality of integrallyformed, triangularly shaped projections having an included angle of fromabout 45* to about 90* projecting from the underside of said spiralscrew thread, said projections having an arcuate shaped outer end; aclosure member having a top portion and a depending skirt portion, saidskirt portion having a continuous spiral groove in its interior walladapted to receive said spiral screw thread and said projections; and atleast one of the group consisting of said container and said closuremember being formed of a resilient plastic material whereby either saidprojections or said spiral groove in said closure member are deformed bycold flow to produce an interlocking between said container and saidclosure member thereby preventing leakage between said container andsaid closure member.